Preparation of Monodisperse Zirconia Particles by Thermal Hydrolysis in Highly Concentrated Solutions

Monodisperse zirconia particles were prepared by the thermal hydrolysis of mixtures of zirconyl chloride, zirconium hydroxide, and water at high concentrations corresponding to about 5 mol/L Zr. The particles, as first prepared, were temporarily agglomerated spheres composed of primary ultrafine zirconia crystals. The agglomerated particles collapsed and dispersed in water to form a translucent sol. When vacuum dried and followed by heat treatment, they were not dispersible. The size of the agglomerated particles increased with increasing molar ratio of the zirconium chloride in the starting mixture, varying from about 0.2 to 0.6 μm. Using the sample thus obtained, monodisperse tetragonal zirconia particles of about 0.35 μm containing 3 mol% Y 2 O 3 with a relatively uniform composition were obtained by homogeneous precipitation of YOHCO 3 by heating with urea and calcination at 800°C.